1. Technical Field
The present invention generally relates to an electrically powered fan assembly.
2. Description of the Related Art
An electronic device generally includes a fan assembly which blows air and discharges heat generated by the electronic device. The fan assembly includes a motor rotating a plurality of rotor vanes to generate air flow. Recently, a high-end electronic device generates considerable heat, and the motor rotating rotor vanes at high speed for discharging more heat is called for.
To increase the rotational speed of the motor, drive current provided to the motor increases as well. Due to the increase of the drive current, some electronic parts of the motor (e.g., coils provided to an armature) generates considerable heat which may damage other electronic parts and degenerate a performance of the motor. To date the following mechanisms have been proposed for cooling a circuit board and coils of the motor used for the fan assembly.
In a conventional motor used for the fan assembly, a stator core and coils provided thereto are arranged at an internal space of a motor casing defined by a rotor unit and a stator unit, and a plurality of rotor vanes are arranged at outside surface of the rotor unit. When the rotor vanes rotate, negative pressure is generated at a gap defined between a stator unit and the rotor unit. Due to the negative pressure, a part of air flow generated by rotation of the rotor vanes is taken into the motor casing through the gap and then the electronic parts within the motor casing are cooled off.
Generally, the stator core and the coils are enclosed inside the motor casing. In the case, the heat generated by the stator core and the coils is accumulated within the motor casing and temperature therein considerably increases. In order to discharge the heat accumulated in the motor casing, air flow taken into the motor casing needs to be increased. In the conventional motor, however, air flow is not actively taken into the motor casing. In the conventional motor using the negative pressure to cool the electronic parts arranged thereon, the air flow taken in the motor casing is limited.